Mr Clifford, speaking on the steps of Belgravia police station, told reporters it was alleged two offences had taken place in 1977.

"These allegations are damaging and totally untrue," he said.

"On a personal level, they are very distressing for myself, my wife and loved ones.

"Anyone who really knew me all those years ago, and those who have known me since, will have no doubt that I would never act in the way I have today been accused."

Mr Clifford - one of the most influential figures in the British media - is the sixth person to be questioned as part of Operation Yewtree, the Met's investigation into allegations, some dating back decades, that have arisen since the late Jimmy Savile was accused of abuse.

The operation has three strands.

One is looking specifically at the actions of Jimmy Savile and the second strand concerns allegations against "Savile and others". The separate third strand relates to alleged complaints against other people unconnected to the Jimmy Savile investigations.

Scotland Yard said Mr Clifford was being investigated under the last strand of Yewtree's investigations.

Five people have now been arrested and a sixth questioned under Yewtree.

The four other people arrested are Freddie Starr, Gary Glitter, Wilfred De'Ath, a retired BBC producer, and radio broadcaster Dave Lee Travis. Police have also questioned under caution a man in his 80s.